Wolfram Mathematica Documentation Center
DOCUMENTATION CENTER SEARCH
New to Mathematica? Find your learning path »
Mathematica > Core Language > Rules & Patterns > Patterns > Condition (/;) >
BUILT-IN MATHEMATICA SYMBOLTutorials »|See Also »|More About »

Condition


is a pattern which matches only if the evaluation of test yields True.

represents a rule which applies only if the evaluation of test yields True.

is a definition to be used only if test yields True.
MORE INFORMATION
  • All pattern variables used in test must also appear in patt.
  • lhs:=Module[{vars}, rhs/;test] allows local variables to be shared between test and rhs. You can use the same construction with Block and With. »
EXAMPLESCLOSE ALL
Basic Examples   (2)
Make a definition with the condition that x should be positive:
Replace all elements which satisfy the condition of being negative:
Make a definition with the condition that x should be positive:
In[1]:=
Click for copyable input
In[2]:=
Click for copyable input
Out[2]=
In[3]:=
Click for copyable input
Out[3]=
 
Replace all elements which satisfy the condition of being negative:
In[1]:=
Click for copyable input
Out[1]=
Scope   (2)
Share a variable between a condition and function body:
Use Condition inside a function body to control evaluation:
New in 1
Ask a question about this page  |  Suggest an improvement  |  Leave a message for the team
Format:   HTML  |  CDF